1. Field
The following description relates to analog radio-over-frequency (RoF)-based mobile fronthaul, and more particularly, to apparatuses and methods for transmitting and receiving a control signal.
2. Description of Related Art
Radio-over-fiber (RoF)-based next generation mobile fronthaul technologies have drawn increasing attention worldwide for their analog signal transmission features which allow for simple configuration and economical construction and operation of networks.
Currently, mobile communication networks use cloud base station architecture that is divided into digital units (DUs) and radio units (RUs), implementing digital optical transmission based on common public radio interface (CPRI)/open base station architecture initiative (OBSAI). However, if the exiting digital-based optical transmission is applied in the 4th generation (4G; LTE/LTE-Z) and 5G mobile communication networks, traffic needed for optical transmission and reception increases several tens of times due to digitalization processes, and hence the current optical transmission scheme may be practically difficult to apply.
The next-generation mobile fronthaul technologies based on analog RoF optical transmission load digital baseband signals for mobile communication on any intermediate frequency (IF) carriers, multiplexes the signals loaded on the IF carriers, and then transmits a multiplexed signal by using an inexpensive directly modulated light source and photodetector, thereby simplifying the design and reducing the cost of a DU/RU platform, as well as preventing degradation of service quality due to latency in digital signal processing. Also, said mobile fronthaul technologies support various types of network topologies, such as point-to-point, star, and ring topologies.
However, since no method for transferring control signals, such as antenna gains and output powers of RUs, which are used to control optical transmission or RUs, has been defined yet, a new method for implementing the control signal transfer in an economical and effective way is needed.
In the exiting mobile fronthaul that utilizes the current CPRI/OBSAI-based digital optical transmission scheme, control information is multiplexed in digital frames in time domain and then used; but in the analog RoF-based mobile fronthaul, if the exiting transmission scheme is used, it is not possible to transmit control information, and thus a new type of control information transmission scheme needs to be defined.